In the late summer there are small brownish insects on birch trees called birch catkin bugs. They feed mainly on the seeds and are harmless to the overall health of the tree. You may find large numbers clustered on a curled leaf, but they do little damage.  Occasionally, these same insects can sneak into homes where they may be a minor nuisance.

Extension Bulletin

 

 

This article was posted in Bugs, Outdoor Insect Invaders.